DENSE HYDROLYSIS PRODUCTS FROM IRON(III) NITRATE AND SULFATE-SOLUTIONS

The hydrolysis of Fe(III) in NO3-3 and SO42- solutions was studied at different temperatures to determine the conditions under which dense Fe(III) precipitates form. Solutions of known composition made from reagent chemicals were maintained in controlled-temperature baths, and changes in color and formation of solid phases were observed as a function of time. Solids were isolated and characterized by X-ray powder diffraction or infrared spectroscopy. Dense Fe(III) precipitates are obtained in Fe(NO3)3 solutions especially at temperatures ≥60°C in acidified solutions. At lower acidities, colloids, a cationic hydrolytic polymer, or gelatinous precipitates form. In SO42--containing solutions a dense amorphous basic ferric sulfate (DABFS) of compositions Fe4(OH) 10SO4·xH2O (x=2 to 3) forms at ≤40°C from solutions with SO42- and Fe3+ concentrations ≤0.2 M and mole ratio SO42- Fe(III)≥0.5. Chemical observations showed that DABFS is related to the Fe (III) cationic hydrolytic polymer. © 1990.